Implement a LOCAL_PEERCRED socket option which returns a
`struct xucred` with the credentials of the connected peer. Obviously this only works (and makes sense) on SOCK_STREAM sockets. This works for both the connect(2) and listen(2) callers. There is precise documentation of the semantics in unix(4). Reviewed by: dwmalone (eyeballed)
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@ -32,7 +32,7 @@
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.\" @(#)unix.4 8.1 (Berkeley) 6/9/93
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.\" $FreeBSD$
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.\"
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.Dd June 9, 1993
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.Dd July 15, 2001
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.Dt UNIX 4
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.Os
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.Sh NAME
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@ -147,6 +147,35 @@ passed to a receiver.
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Descriptors that are awaiting delivery, or that are
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purposely not received, are automatically closed by the system
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when the destination socket is closed.
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.Pp
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The effective credentials (i.e., the user ID and group list) the of a
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peer on a
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.Dv SOCK_STREAM
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socket may be obtained using the
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.Dv LOCAL_PEERCRED
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socket option.
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This may be used by a server to obtain and verify the credentials of
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its client, and vice versa by the client to verify the credentials
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of the server.
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These will arrive in the form of a filled in
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.Ar struct xucred
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(defined in
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.Pa sys/ucred.h ) .
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The credentials presented to the server (the
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.Xr listen 2
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caller) are those of the client when it called
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.Xr connect 2 ;
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the credentials presented to the client (the
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.Xr connect 2
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caller) are those of the server when it called
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.Xr listen 2 .
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This mechanism is reliable; there is no way for either party to influence
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the credentials presented to its peer except by calling the appropriate
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system call (e.g.,
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.Xr connect 2
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or
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.Xr listen 2 )
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under different effective credentials.
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.Sh SEE ALSO
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.Xr socket 2 ,
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.Xr intro 4
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@ -51,7 +51,7 @@
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static struct protosw localsw[] = {
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{ SOCK_STREAM, &localdomain, 0, PR_CONNREQUIRED|PR_WANTRCVD|PR_RIGHTS,
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0, 0, 0, 0,
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0, 0, 0, &uipc_ctloutput,
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0,
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0, 0, 0, 0,
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&uipc_usrreqs
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@ -91,6 +91,7 @@ static void unp_scan __P((struct mbuf *, void (*)(struct file *)));
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static void unp_mark __P((struct file *));
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static void unp_discard __P((struct file *));
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static int unp_internalize __P((struct mbuf *, struct proc *));
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static int unp_listen __P((struct unpcb *, struct proc *));
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static int
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uipc_abort(struct socket *so)
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@ -199,7 +200,7 @@ uipc_listen(struct socket *so, struct proc *p)
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if (unp == 0 || unp->unp_vnode == 0)
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return EINVAL;
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return 0;
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return unp_listen(unp, p);
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}
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static int
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@ -434,6 +435,41 @@ struct pr_usrreqs uipc_usrreqs = {
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uipc_send, uipc_sense, uipc_shutdown, uipc_sockaddr,
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sosend, soreceive, sopoll
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};
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int
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uipc_ctloutput(so, sopt)
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struct socket *so;
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struct sockopt *sopt;
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{
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struct unpcb *unp = sotounpcb(so);
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int error;
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switch (sopt->sopt_dir) {
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case SOPT_GET:
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switch (sopt->sopt_name) {
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case LOCAL_PEERCRED:
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if (unp->unp_flags & UNP_HAVEPC)
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error = sooptcopyout(sopt, &unp->unp_peercred,
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sizeof(unp->unp_peercred));
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else {
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if (so->so_type == SOCK_STREAM)
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error = ENOTCONN;
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else
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error = EINVAL;
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}
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break;
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default:
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error = EOPNOTSUPP;
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break;
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}
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break;
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case SOPT_SET:
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default:
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error = EOPNOTSUPP;
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break;
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}
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return (error);
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}
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/*
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* Both send and receive buffers are allocated PIPSIZ bytes of buffering
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@ -609,7 +645,7 @@ unp_connect(so, nam, p)
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register struct sockaddr_un *soun = (struct sockaddr_un *)nam;
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register struct vnode *vp;
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register struct socket *so2, *so3;
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struct unpcb *unp2, *unp3;
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struct unpcb *unp, *unp2, *unp3;
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int error, len;
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struct nameidata nd;
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char buf[SOCK_MAXADDRLEN];
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@ -648,12 +684,40 @@ unp_connect(so, nam, p)
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error = ECONNREFUSED;
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goto bad;
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}
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unp = sotounpcb(so);
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unp2 = sotounpcb(so2);
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unp3 = sotounpcb(so3);
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if (unp2->unp_addr)
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unp3->unp_addr = (struct sockaddr_un *)
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dup_sockaddr((struct sockaddr *)
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unp2->unp_addr, 1);
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/*
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* unp_peercred management:
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*
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* The connecter's (client's) credentials are copied
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* from its process structure at the time of connect()
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* (which is now).
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*/
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memset(&unp3->unp_peercred, '\0', sizeof(unp3->unp_peercred));
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unp3->unp_peercred.cr_uid = p->p_ucred->cr_uid;
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unp3->unp_peercred.cr_ngroups = p->p_ucred->cr_ngroups;
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memcpy(unp3->unp_peercred.cr_groups, p->p_ucred->cr_groups,
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sizeof(unp3->unp_peercred.cr_groups));
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unp3->unp_flags |= UNP_HAVEPC;
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/*
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* The receiver's (server's) credentials are copied
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* from the unp_peercred member of socket on which the
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* former called listen(); unp_listen() cached that
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* process's credentials at that time so we can use
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* them now.
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*/
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KASSERT(unp2->unp_flags & UNP_HAVEPCCACHED,
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("unp_connect: listener without cached peercred"));
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memcpy(&unp->unp_peercred, &unp2->unp_peercred,
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sizeof(unp->unp_peercred));
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unp->unp_flags |= UNP_HAVEPC;
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so2 = so3;
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}
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error = unp_connect2(so, so2);
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@ -1244,6 +1308,21 @@ unp_dispose(m)
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unp_scan(m, unp_discard);
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}
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static int
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unp_listen(unp, p)
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struct unpcb *unp;
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struct proc *p;
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{
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bzero(&unp->unp_peercred, sizeof(unp->unp_peercred));
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unp->unp_peercred.cr_uid = p->p_ucred->cr_uid;
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unp->unp_peercred.cr_ngroups = p->p_ucred->cr_ngroups;
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bcopy(p->p_ucred->cr_groups, unp->unp_peercred.cr_groups,
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sizeof(unp->unp_peercred.cr_groups));
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unp->unp_flags |= UNP_HAVEPCCACHED;
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return (0);
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}
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static void
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unp_scan(m0, op)
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register struct mbuf *m0;
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@ -46,12 +46,16 @@ struct sockaddr_un {
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char sun_path[104]; /* path name (gag) */
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};
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/* Socket options. */
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#define LOCAL_PEERCRED 0x001 /* retrieve peer credentails */
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#ifdef _KERNEL
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struct mbuf;
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struct socket;
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int uipc_usrreq __P((struct socket *so, int req, struct mbuf *m,
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struct mbuf *nam, struct mbuf *control));
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int uipc_ctloutput __P((struct socket *so, struct sockopt *sopt));
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int unp_connect2 __P((struct socket *so, struct socket *so2));
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void unp_dispose __P((struct mbuf *m));
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int unp_externalize __P((struct mbuf *rights));
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@ -38,6 +38,7 @@
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#define _SYS_UNPCB_H_
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#include <sys/queue.h>
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#include <sys/ucred.h>
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/*
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* Protocol control block for an active
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@ -80,8 +81,26 @@ struct unpcb {
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int unp_cc; /* copy of rcv.sb_cc */
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int unp_mbcnt; /* copy of rcv.sb_mbcnt */
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unp_gen_t unp_gencnt; /* generation count of this instance */
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int unp_flags; /* flags */
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struct xucred unp_peercred; /* peer credentials, if applicable */
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};
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/*
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* Flags in unp_flags.
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*
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* UNP_HAVEPC - indicates that the unp_peercred member is filled in
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* and is really the credentials of the connected peer. This is used
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* to determine whether the contents should be sent to the user or
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* not.
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*
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* UNP_HAVEPCCACHED - indicates that the unp_peercred member is filled
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* in, but does *not* contain the credentials of the connected peer
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* (there may not even be a peer). This is set in unp_listen() when
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* it fills in unp_peercred for later consumption by unp_connect().
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*/
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#define UNP_HAVEPC 0x001
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#define UNP_HAVEPCCACHED 0x002
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#define sotounpcb(so) ((struct unpcb *)((so)->so_pcb))
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/* Hack alert -- this structure depends on <sys/socketvar.h>. */
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